A h ybrid image-intensier tube, suitable for extremely low-light imaging, has been tested. This device is based on an Electron-Bombarded CCD chip (EBCCD) with 1024 1024 sensitive pixels. The tube, which has a photocathode diameter of 40 mm, is gateable and zoomable, with an image magnication varying from 0.62 to 1.3. The high gain (about 4000 collected electrons per photoelectron at the operational voltage of 15 kV) and the relatively low noise (180 electrons per pixel at 10 MHz pixelreadout frequency), allows single-photoelectron signals to be separated from noise with a signal-to-noise ratio greater than 10. By applying an appropriate threshold on the signal amplitude, the background can almost be eliminated, with a loss of few percent in single-photoelectron counting. High inner gain, low noise, single-photoelectron sensitivity, and high spatial resolution make the EBCCD imaging tube a unique device, attractive for many applications in high-energy physics, astrophysics, biomedical diagnostics.

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A number of time analysing image converter tubes integrated with thinned, backside illuminated,electron bombarded (EB) CCDs was developed. Among them are PVOO 1 , PVOO3 , and PIFO 1 streak tubes differing from each other by their internal electron optics and external (metal-glass or metal-glass-ceramic) geometry. All tested EB CCD/streak tubes reveal a relatively good behaviour refering to the long term stability of their input S 1 photocathode and reproducibility of the matrix parameters. These tubes advantageously differ from their regular type, phoshor screen analogoues by rather high spatial resolution ( >40 lp/mm at 10% MTF for PV tyje tubes and >25 lp/mm at 10% MTF for PIF type tubes) , reasonably good threshold sensitivity of 10 J/cm2 in standard, 10 MHz CCD scanning mode at 850 nm input radiation, picosecond temporal resolution ( better 5 ps) at relatively acceptable value of the light transfer function ( -102). 2.INTRODUCTIONAmong problems in picosecond streak image technique which require fast solution, let us mention the followings: to simplify streak cameras maintaining, to match them with a personal computer in order to automate the process of quantative data recording processing and presentation, to improve streak systems realiability, and to reduce their cost. A promising approach in solving of some of the mentioned problems consists in replacing traditional luminescence screen in streak image tubes by a thinned, backside illuminated, electron bombarded (EB) 2 The rear face bombardment by 5-20 keY photoelectrons makes the detection of every incident electron a possibility3 due to high EBS gain in silicon, ranging from 50 to 3 .5 • 1o. Since the EBS cascade process takes place close to the rear face, it becomes necessary to thin the CCD up to 8-15 m in order to conserve both sensitivity and spatial resolution46.The replacement of phosphor screen with EB CCD sensors was successfully demonstrated by various group of authors who have developed a set of very sensitive image intensifiers for low light level vision79. However, to our knowledge, almost no reports besides a paper of J.C.Cheng et were published on EB CCD introduction in a vacuum body of ultrafast streak tubes.In 1988 we have presented our first experimental results on fabrication and static measurements of a picosecond streak tube incorporated with a thinned, backside illuminated EB CCD matrix2. Spatial resolution of our integrated EB CCD/PVOO3 tube was better than 40 lp/mm and its sensitivity was much higher than the sensitivity of the same tube but supplied with a regular luminescence screen These experiments encouraged us to continue investigations in designing a reliable and reproducible EB 94

It is well known that thinned backside illuminated CCD image sensors are very efficient for electron beam imaging. We have adapted our electron-bombarded (EB) CCD for application in UV and VUV spectral regions. This adaptation includes the creation of shallow accumulation layer near the device backside surface either by ion implantation and annealing or by a certain chemical treatment of the surface. Preliminary experimental results confirm the applicapability of the developed procedure in achieving a reasonable quantum efficiency. Some problems associated with the UV and VUV imagers design and fabrication are discussed.

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